Art of coal drying



2 Sheets-Sheet l Original Filed Nov 17, 1949 ATTORNEYS April 16, 1957 R.G. TUCKER 2,788,585

ART OF COAL DRYING original Filed Nov. 17, 1949 2 sheeis-sheei 2INVENTOR @MJKM @n1/MPM ATTOR NEYS United States Patent O ART F COALDRYING Robert G. Tucker, Chicago, Ill., assignor to CombustionEngineering, Inc., New York, N. Y., a corporation of DelawareContinuation of abandoned application Serial No.

127,897, November 17, 1949. This application 0ctober 22, 1953, SerialNo. 387,742

This invention relates to comminuted coal drying and separating systemsin which wet comminuted' coal is delivered into a stream of highvelocity hot gases in which the coal particles are substantiallyinstantaneously dried and the gases and coal particles carried therebyare delivered into a separator and collector, such as a cyclone, whereinthe now moisture-laden gases are separated from the dried coal.

In such conventional systems, the wet comminuted coal is deliveredlaterally into the lower end of a tall upright drying column and thehigh velocity hot drying gas is delivered into the said end of thecolumn closely adjacent to the point of coal admission. In consequence,the temperature of the drying gas is quickly reduced in the vicinity ofthe point of wet coal admission, with concomitant reduction in thevolume and therefore of the velocity of the gas. In consequence, thepick-up of coal particles and the eiciency of the system arecorrespondingly lowered.` Particles of coal, not carried upwardlythrough the column, separate out by gravity and are removed, preferablyperiodically. For reasons above pointed out, the amount of coal soseparating is unduly large because of the relative ineciency of thepickup.

The objective of the present invention is to render such systems moreeicient by increasing the pick-up of coal particles by the incoming hotdrying gases, thereby ensuring a maximum delivery of coal particles tothe cyclone and diminishing the quantity of coal which separates out bygravity as aforesaid.

More specifically stated, the invention resides in providing the hot gasdelivering parts with a high velocity pick-up section, so relativelyconstructed and arranged (a) as to be relatively unaffected by thesudden drop in temperature and therefore decrease in volume of the hotdrying gases which occur at the region where the wet comminuted coal isdelivered into the column, and (b) as to ensure adequate acceleration ofupward movement of the heavier particles. In consequence, the coalparticles have maximum momentum, ensuring greatly in creased pick-up andincreased coal delivery to the cyclone. The parts are also arranged andconstructed as to secure low pressure drop.

How the foregoing, together with such other objects and advantages asmay hereinafter appear or are incident to the invention are realized, isillustrated in the accompanying drawings, wherein:

Fig. 1 is a diagrammatic side elevation of a drying system embodying myinvention;

Fig. 2 is an enlarged cross sectional view illustrating certain detailsof the invention, and

Fig. 3 is a view somewhat corresponding to Fig. 2 but illustrating amodification of the invention.

Referring now to Fig. 1, the reference character A denotes a furnace forsupplying hot drying gases, such, for example, as hot air; the referencecharacter B denotes the drying tower or column; the reference characterC, the cyclone separator; the reference character D, the

bin for comminuted coal; and the reference character E, the feeder fordelivering the wet coal into inlet B 1ocated near the bottom of thecolumn B.

The reference character F indicates a starting stack and the referencecharacter G indicates, as a whole, a hot gas delivering and coalcollecting chamber, for dclivering the hot gases to the open lower endof the column B and for collecting such particles of the coal as are notcarried upwardly through the column by the hot gases and which fall outby gravity. The hot gases from furnace A are delivered to chamber G bymeans of the pipe or conduit 7.

The cyclone C has an outlet 8 for the moisture laden gases from whichthe coal has been separated in the separator, which outlet is providedwith a fan 9 for drawing the gases through the system.

At the bottom the cyclone is provided with an outlet 1t? provided with aconventional air lock 11 below which there is a conveyor 12 for the drycoal. The wet coal is fed to the bin D by means of the conveyor 13.

Column B, chamber G, and conduit 7` are preferably circular in crosssection.

Referring now to chamber G, this comprises a main portion 14- having aflanged inlet 15 adapted to be coupled to the conduit 7 in conventionalmanner.

At the upper end of the chamber G is a pick-up section 16 which has aninternal diameter relatively substantially smaller than the internaldiameter of the main portion 14 of the chamber. The pick-up section hasa straight bore. The upper portion 17 of the main chamber 14 is taperedpreferably at a 60 angle to merge with the pick-up reaction to reducepressure drop. The lower end 18 of the main portion 14 is preferablytapered to a discharge opening 19.

The upper end of the pick-up section 16 registers with the lower openend of the column B and is secured thereto in any conventional manner.

The chamber G and the conduit 7 are desirably refractory lined so as towithstand the high temperatures of the hot gas discharging therethroughfrom the furnace A.

The internal diameter of the pick-up section 16 preferably approximatesthe internal diameter of the column B, and the internal diameter of theconduit 7 and the inlet 15 are preferably substantially the same as theinternal diameter of the main portion 14 of the chamber G. In theembodiment illustrated, the internal diameter of the pick-up section 16is 2 feet 8 inches, and the internal diameter of the outlet 19 of thechamber G is l foot. From these the proportions of the remaining partsof the particular installation can be readily ascertained.

It will Ibe observed that the vertical length of the piclcup section issubstantial, roughly approximating the internal diameter of the pick-upsection.

The operation is as follows:

The fan 9 has a capacity sufficient to draw the hot gases through thesystem at relatively high. veloci-ty. The gases leave the furnace A atrelatively high temperature (of from about 1000D F. to about 1500 13.),and therefore in relatively greatly expanded condition. By reason of therelatively large size of the internal diameter of the conduit 7 and thechamber G, adequate volume of gases is provided for deliverytherethrough with comparatively low pressure drop. The velocity of thegases is greatly increased in the pick-up `section because of itsrestricted size. In the particular installation shown, with coalparticles (generally ranging downward from Vs" size), the velocity ofthe gases passing through the pick-up section is desirably in theneighborhood of 10,000 feet per minute. As pointed out, the pick-upsection has substantial vertical length, that is to say, the bottomthereof is well below the bottom of the column B and Ihence well belowr`the feeder E.Ak whichv discharges the wet coal into the column.

By the introduction of the wet coal and the substantial instantaneousevaporation of moisture, the temperature of the gases at the point ofwet fuel admission isquickly lowered, and in consequence Vthe volume ofthe gases is decreased and the velocity of the gases through the columnis reduced, say to the neighborhood of 5500 feet per minute. However,because the pick-up section extends well ibelow the end of the columnand therefore ybelow the point ol coal admission, there is a zone inwhichv the high veloci-ty stream of gases is formed and well establishedbefore coal is delivered thereto, and the gases passing through thepick-up section are not appreci'a'bly cooled' and maintain theirvelocity. yto heavy particles of coal laterally introduced into thecolumn, these, of course, accelerate slowly and normally tend to drop bygravity. Because of the depth of the pick-up section, it is ensured thatany such heavy particles as tend to drop through the pick-up sectionhave their downward movement arrested and have an upward movementimparted thereto sufliciently accelerated to give the impetus necessaryto carry them through the system. Thus, the pick-up section is veryeffective and a maximum amount of coal is picked up and carried upwardlythrough the drying column to the cyclone separator.

The system will effectively handle comminuted coal in particle sizesranging from about down to 'the lowest mesh coal produced.

The heavy particles which are not carried through the system aredischarged through outlet 19 by means of a conventional double valve 2i)which permits ,the discharge thereof without introducing air into the-systemM A damper 21 may be provided for introducing tempering air intoconduit 7. The bin D is provided with a conventional gate 22.

Referring now to the modification shown in Fig. 3, the chamber G has notapered upper section bu-t has a straight bore. The pick-up section 16in this instance is separate and consists of a tube llaring somewhat atthe its bottom. Surrounding the lower end of the pick-up section 16 isan annular sealing device 23 carried by the top closure member 2.4 forthe chamber G. The pick-up section 16 is free to slide with respect tothe seal 23 and therefore can expand and contract. The pick-up sectionlo has a flanged coupling 25 which is complementary to the flangedcoupling 26 at the lower end of theV inlet B for detachable connection,as lby nuts and bolts not shown. The length `of the pick-up section 16may be adjusted by undoing the couplings and inserting a filler membertherebetween.

The additional advantages of the modification are that standard kilntile may be used as a liningv for the chamlber G; no difiiculties areencountered from expansionand contraction; and the pick-up section maybe adjusted in length to aiford greater flexibility with respect to thekind of coai which may be handled.

This application is a continuation of Serial No. 127,897, filedNovemberV 17, 19,49, now abandoned.

I claim:

A method of flash drying coal to improve pickup eciency comprising thesteps: forming a vertically rising stream yof hot gas moving at apredetermined velocity; increasing the velocity of the gas stream andsubstantially maintaining the velocity over a predetermined verticaldistance; and feeding Wet coal into saidstrearn above the point wherethe velocity is initially increased, the point of said feeding 'beingsuch that the high velocity gas stream operates to dry substantially allof any coal falling downwardly therethrough sufiicientlybefore the coalreaches the point where the velocity is initially increased so that theforce yof the gas on the dried coal is ,sufficient to reverse itsdirection and move the same upwardly.

References Cited in the le of this patent UNITED STATES PATENTS.1,550,992 Trump Aug. 25, 1925 2,296,159 Gordon sept. 15, 1942 2,538,833De Rycke 1an. 23, 1951

